1. Field of the Invention
The present invention generally relates to a high-throughput semiconductor-processing apparatus equipped with multiple dual-chamber modules.
2. Description of the Related Art
In the field of CVD apparatuses and etcher apparatuses for treating substrates such as semiconductor wafers, improvement on the productivity or throughput is one important factor. For example, U.S. Pat. No. 6,074,443 teaches a total of four reaction chambers. As shown in FIG. 10, the equipment consists of a preclean chamber 1002 and reaction chambers 1004, 1006 attached to a central chamber 1010 with a transport mechanism 1012, and each processing chamber contains sub-chambers 1002A and B, 1004A and B, and 1006A and B, respectively (the total of reaction sub-chambers is four). Wafers are transferred to wafer cassettes 1008A and B within a load lock 1008. In the apparatus, processing time can be shortened, and productivity can be improved.
However, although wafer-handling time (required for unloading/loading a pair of wafers from/to a reaction chamber and moving onto a next reaction chamber) has been getting shorter, due to operational limits of servomotors, friction between wafers (silicon, glass, etc.) and handling materials (ceramics, metal, etc.) for supporting wafers, etc., the wafer-handling time is getting close to its limit, e.g., about 20 seconds when transferring a pair of wafers simultaneously. As described above, although the wafer-handling time is shortened, process time is not significantly shortened. For example, it generally takes about 60 to about 80 seconds for thin film processing associated with downsizing of devices and tendency of finer structures (e.g., in general, a thickness of about 50 nm to about 350 nm by standard plasma CVD). Thus, conventionally, the wafer-handling robot is not fully and continuously in operation and waits for the reaction chambers to complete processing. Although the apparatus shown in FIG. 10 has three sides for attaching chambers thereto, one chamber thereof is for precleaning, and thus, effectively, only two sides (four sub-chambers) are used for deposition. Thus, in the conventional apparatus, the wafer-handling robot is not fully and continuously in operation and waits for the sub-chambers to complete processing. Further, because a sub-chamber for precleaning is used, it is difficult to simplify, regulate, and speed up transferring wafers by the wafer-handling robot. Even if the sub-chambers for precleaning are used as those for deposition, three sides (six sub-chambers) are used at maximum.
The sequence when three sides are used is illustrated in FIG. 5. When three modules (three sides) are connected to a wafer-handling chamber, if the ratio of handling time to process time is either about ⅓ or about ¼, there is dead time, i.e., a back end robot waits for the first/second module to finish processing wafers, although the back end robot finishes unloading/loading wafers from/to the third module and is ready to unload the processed wafers from the first/second module. Further, practical maintenance of the modules and the wafer-handling chamber and sequences of deposition rotation need to be considered.
Except FIG. 10 itself, any discussion of problems and solutions involved in the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion were known at the time the invention was made.